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speedo help to stop speeding tickets

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by zakk, Oct 1, 2001.

  1. zakk

    zakk 1/2 ton status

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    i got an alleged ticket for doing 60+ in a 45 even though my truck does not even get to 60...that is why i was working on it all weekend. i need help fixing the speedo so that i can make sure i am not speed once i get my truck fixed. Is there a co. that makes new speed gears? can it be recalibrated??
    personally i think i was ticked for DWB (driving while brown) cuz she made me get out and asked when i was last in San Deigo cuz a truck like mine was stolen...i digress...

    -Zakk
    '77 K5 SB 400 TH350 NP203 p/t 6" Lift D60 14BFF 4.10's 36"Wrangler II's
     
  2. xnoahx

    xnoahx 1/2 ton status

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    Im pretty sure you can get new speedo gears from a chevy dealer. And im not sure about this but i think a trans shop should be able to calibrate it but i might be wrong

    My 73 K5 <a target="_blank" href=http://www.geocities.com/xk5blazerx/73k5.htm>http://www.geocities.com/xk5blazerx/73k5.htm</a> 350/TH350/NP203, Q-jet, Edelbrock intake, Vortec heads, 4" lift, and 36" TSL's
     
  3. chevyfumes

    chevyfumes Court jester

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    Watch for the muzzleflash!
    Try this,<a target="_blank" href=http://http:/dorianyeager.com/gearcalc.html>http:/dorianyeager.com/gearcalc.html</a>

    <font color=blue> I'd rather have a bottle in front of me, than a frontal lobotomy!
     
  4. chevyfumes

    chevyfumes Court jester

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    Watch for the muzzleflash!
    HMMM, I did something wrong... Ask dyeager I got it from his site...

    <font color=blue> I'd rather have a bottle in front of me, than a frontal lobotomy!
     
  5. AGM73k5

    AGM73k5 1/2 ton status

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    <a target="_blank" href=http://dorianyeager.com/gearcalc.html>dorianyeager.com/gearcalc.html</a> &lt;-- Should work :)

    -Aaron

    ___ __ _ _ ____ __
    AGM73k5 -- ajgm1@yahoo.com
     
  6. zakk

    zakk 1/2 ton status

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    thanks...i will have to call around. i really need this fixed =o)

    -Zakk
    '77 K5 SB 400 TH350 NP203 p/t 6" Lift D60 14BFF 4.10's 36"Wrangler II's
     
  7. Pure Insanity

    Pure Insanity 1/2 ton status

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    Why dont you just get paced by a car or truck that is dead stock, and find out how far off you are? Then just adjust your driving speed accordingly. I have been doing that for 15 yrs, and have yet to get a ticket. No need to change anything or have it recalibrated. I know this is not the CORRECT way to do it but its fool proof. If your "pace car" is registering 55 but you are at 40, there is a 15 MPH difference. Problem solved. And yes it will be the same no matter what gear you are in. The speedo will be the same no matter what gear you are in. I only say that because I have had to debate it in the past and figured Id head it off at the pass, in case you were gonna ask.[​IMG]

    If ya can't stop.......Smile as you go under! [​IMG]
     
  8. xnoahx

    xnoahx 1/2 ton status

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    sorry, it will be different, if your speedo reads 15 you arent going 30, the speed is off by a certain percent, the faster you go, the more its off. like for every MPH you are going, its is actually going 1.2 or something. so for every 5 mph you are going 1 mph faster than the reading. 5=6 10=12 15=18 20=24 25=30 30=36 and so on. at 50 on the speedo you will be going 60. But this all depends on how much its off. check out the links on this post to see how much its off.

    My 73 K5 <a target="_blank" href=http://www.geocities.com/xk5blazerx/73k5.htm>http://www.geocities.com/xk5blazerx/73k5.htm</a> 350/TH350/NP203, Q-jet, Edelbrock intake, Vortec heads, 4" lift, and 36" TSL's
     
  9. chevyfumes

    chevyfumes Court jester

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    What he said

    <font color=blue> I'd rather have a bottle in front of me, than a frontal lobotomy!
     
  10. Pure Insanity

    Pure Insanity 1/2 ton status

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    So what your saying is a speedo is off in a stock rig too! UH UH! It will be consistant. If its off by x its off by x at ANY speed. Been there, done that, tried it, and tested it at different speeds. If your rig does that from the factory, OK, but all you have done is changed the final drive ratio, which will change the speedo reading.

    If ya can't stop.......Smile as you go under! [​IMG]
     
  11. AGM73k5

    AGM73k5 1/2 ton status

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    So if I'm going 5 according to my speedo and I'm 15 mph off then I'm really going 20? And if the speedo says 1 then I'm really going 16? So then my speedo won't move until I get up to 15mph?
    I'm just trying to make sure I've got this right because I don't really want to spend money to recalibrate if I don't have to :)
    -Aaron

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    AGM73k5 -- ajgm1@yahoo.com
     
  12. Scooter

    Scooter 1/2 ton status

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    Actually xnoahx is right. You are incorrect in the 1st part of your statment of: <blockquote><font class="small">In reply to:</font><hr>

    If its off by x its off by x at ANY speed. Been there, done that, tried it, and tested it at different speeds.

    <hr></blockquote> But you have it right at the end of your statement" <blockquote><font class="small">In reply to:</font><hr>

    all you have done is changed the final drive ratio, which will change the speedo reading.

    <hr></blockquote> The speedo will consistently be off by the % of the change.

    Back when I had my mustang I changed out the gears from 2.73 to 3.55. That was a 30% difference in the gear ratio. At that time I was good friends with some cops and had them use their radar to check the speeds. The speedo was consistently 30% faster than the radar reading. To keep speeds at or near the posted limits I had to add 30% to the posted speed limit and that was what I ran the car at according to its speedo.

    For example: posted speed limit is 60 MPH, add 30% to the posted limit (18MPH for this example) and you get 78MPH. Run the car at 78MPH according to the speedo and you'd be really close to the speed limit. But if the posted limit was 30 MPH you would only adjust by 9MPH not 18. If I used your idea that it is always off the same MPH at any speed and I only checked the speed at 60MPH, when I got into the 30MPH zone I'd be speeding by 9MPH.

    Unfortunately it also added miles to the odometer 30% faster too.[​IMG] See, its a ratio thing .. [​IMG][​IMG]

    Scot in KC, MO.
    <a target="_blank" href=http://www.off-road.ws/images/users/Scooter/side_right_2.jpg>Blue 87 GMC Jimmy</a>
    Red 86 Toyota 4Runner (for sale $2000 obo)
     
  13. Pure Insanity

    Pure Insanity 1/2 ton status

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    I have gone to several gear calculators, I just cannot find a way to explain what Im getting at. Basicly, if the speedo will gain in stock form it will gain in modified form. If its accurate in stock it will be accurate in modified. Its all consistant mechanical changes. If you have differences like that, the speedo cannot be counted on in anything. Stock, modified, Stock modified, or modified stock. X is X and always will be X. If that were the case, why do they only have 1 way of correcting speed, on the calculators? A tire change is the same as a gear change, and vice versa. Consistant change both ways.

    If ya can't stop.......Smile as you go under! [​IMG]
     
  14. xnoahx

    xnoahx 1/2 ton status

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    That stinks on the milage thing. The bigger gears are just the opposite of larger tires with the speedo, the tires slow it down and the gear raise it up. so my odometer reads less than what there really is. its a pain trying to figure gas milage

    My 73 K5 <a target="_blank" href=http://www.geocities.com/xk5blazerx/73k5.htm>http://www.geocities.com/xk5blazerx/73k5.htm</a> 350/TH350/NP203, Q-jet, Edelbrock intake, Vortec heads, 4" lift, and 36" TSL's
     
  15. Pure Insanity

    Pure Insanity 1/2 ton status

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    Scooter has explained it in a way that I understand, but yet confuses me! How have I gotten away w/ driving past cops in my rig that was 20 MPH off and NEVER gotten a ticket? You will prob never get a ticket for going too slow, but you will get them for going too fast. This just doesnt make sense. UNLESS tire growth plays a part. I get what your saying but yet I dont. I have passed cops in a 60 zone, reading 40, and never been hasseled. According to what you said I should have been MOVING faster than my 20 off , and gotten a ticket. I seen him pointing the radar gun at me so I knew he got me. Final drive is final drive. It just doesnt make sense.

    If ya can't stop.......Smile as you go under! [​IMG]
     
  16. J.C.Staley

    J.C.Staley Registered Member

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    I'm the lazy sort. I used my GPS to tell me how fast I'm going. It works really well. I just told my daughter as long as she is 5 MPH under the speed limit in town she should be ok.
     
  17. Pure Insanity

    Pure Insanity 1/2 ton status

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    If thats the case why do they call it final drive? and not final drive plus or minus %?

    If ya can't stop.......Smile as you go under! [​IMG]
     
  18. xnoahx

    xnoahx 1/2 ton status

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    The problem is when you change to a different tire size or gear set your speedo gears arent accurate any longer. You can get different gears in your tranny that will fix the speedo or you can try to get the tires and gearing to match the stock setup

    My 73 K5 <a target="_blank" href=http://www.geocities.com/xk5blazerx/73k5.htm>http://www.geocities.com/xk5blazerx/73k5.htm</a> 350/TH350/NP203, Q-jet, Edelbrock intake, Vortec heads, 4" lift, and 36" TSL's
     
  19. 84_Chevy_K10

    84_Chevy_K10 Banned

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    My truck had 2.73s stock and 29" tires

    Now it has 4.10s and 35" tires.

    Think my speedo's a little goofy? Yep. I just drive slow. I use the tach on the highway. In town, I drive about 5 mph over the speed limit on my speedo, which is close enough for me to not get pulled over.

    I'm fixing my speedo when I swap in my SM 465/NP 205 though.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  20. Pure Insanity

    Pure Insanity 1/2 ton status

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    OK guys, I have to give up the fight. I went to Dorians speedo calc. and punched in 31 and 38 @ 30 and it was 6 MPH difference. @ 60 it was 12. So I dont know what to say at this point other than how in the world have I not gotten a ticket in 15 yrs of big trucks?! It still makes sense, but still doesnt! But I cant argue w/ a calculator.

    SOOO......DISREGARD MY 1ST POST! I WAS WRONG!!! I guess youll just have to recalibrate( and so will I )[​IMG]

    I still wanna know how I have not gotten a ticket. If I was 20 off @ 30 I in theory should have been 40 off at 60. There is NO WAY I was doing 100 in that thing at times. I would try to explain the ratios but it was a Jeep my dad bought wrecked that the front shaft was shoved thru the T-case, breaking the tranny and case and he replaced them from different Jeeps. Then we put different axles in to it later that had different gears than was in the stock axles, and added the 38s. So basicly the case speedo gear was not right for the speedo, and then the gears in the later added axles were wrong to both, on top of the tire difference, which made a total mess![​IMG] How did a long haired 16 yr old in a CJ on 38s w/ full size axles NOT get a ticket?[​IMG]

    I give up/ give in, yall are right.

    But dont ya love a debate!?!? LOL!

    If ya can't stop.......Smile as you go under! [​IMG]
     

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